Cutting the Sash Joints

The 18th-century study behind this module found the most natural order for a joiner: cut all the joints on square stock first, then plane the glass rebates, then mould the profiles ¹. These first two days are the joints.

Orient and square

North House starts from pre-milled stock ². Plane each piece square and to exact width and thickness; every member of a sash must be the same thickness or the faces won’t flush. Then orient the grain. On the Stiftsgården sashes the pith side faces outward and toward the center of the sash ¹. Norwegian practice describes window parts as seen from the outside, and Norwegian tools and benches are right-handed ¹. Mark each piece’s face and edge.

Lay out

Clamp the stiles together and the rails together and mark them as pairs from the rod:

• the outer ends;
• the light lines, the inside edges of the pane openings;
• the rebate depth and the depth of the moulding.

Every dimension comes from the light size, and each bar mortise runs from the light line to the top of the profile ¹. Set a mortise gauge to the tenon thickness (a third of the stock is the usual rule of thumb) and gauge every joint from the face side.

Corner joints

The corners are open mortise and tenon joints, a slot in one member and a tenon on the other, like a bridle ¹:

1. Saw the tenon cheeks on the rail ends, on the waste side of the gauge lines, and saw the shoulders.
2. Saw down both sides of the slot in the stile end, then chop out the waste with a chisel from both faces toward the middle.
3. Pare to fit: the tenon should slide in with hand pressure.
4. Leave the moulded and rebated portion of each shoulder long for now; it gets cut back when you mitre the moulding.

At Stiftsgården each corner was locked with two square pegs, 8 by 8 mm, driven from the interior face ¹. You’ll drill for them at assembly.

Bar joints

The bars are about 1 inch wide ¹. At Stiftsgården the horizontal bars were tenoned into the stiles, and the vertical bar was made in separate pieces, one between each rail and bar, each tenoned at both ends ¹. For a four-pane sash you can follow that, or run the vertical bar full length and halve it across the horizontal one, each bar cut half-depth where they cross. North House’s description mentions only “a crossed vertical and horizontal bar” ², so either is defensible.

Mortises for the bars run from the light line to the top of the profile, as laid out. Cut tenons on the bar ends a hair long and trim to fit.

Pace

Heiberg’s team found an experienced joiner makes about one sash a day at a calm pace, two with practice ¹. Two days for the joints of a first sash is ordinary.

Try it

Cut one corner joint in scrap before the real stock. Check that the tenon’s shoulders close tight on both faces at once; a gap on one face means the shoulder isn’t square to the face.